Return from subroutine, with enhanced pointer authentication using a register
This instruction authenticates the address that is held in LR, using SP as the first modifier, the value in the specified register as the second modifier, and the specified key, and branches to the authenticated address.
Key A is used for RETAASPPCR. Key B is used for RETABSPPCR.
If the authentication passes, the PE continues execution at the target of the branch. For information on behavior if the authentication fails, see Faulting on pointer authentication.
The authenticated address is not written back to LR.
This instruction provides a hint that this is a subroutine return.
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | M | 1 | 1 | 1 | 1 | 1 | != 11111 | ||||
| opc | op2 | Rn | Rm | ||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_PAuth_LR) then EndOfDecode(Decode_UNDEF); end; let m : integer = UInt(Rm); let use_key_a : boolean = M == '0'; let auth_then_branch : boolean = TRUE;
var inst_type : GCSInstruction; var target : bits(64) = X{}(30); let modifier : bits(64) = SP{}(); let modifier2 : bits(64) = X{}(m); if use_key_a then target = AuthIA2(target, modifier, modifier2, auth_then_branch); else target = AuthIB2(target, modifier, modifier2, auth_then_branch); end; if IsFeatureImplemented(FEAT_GCS) && GCSPCREnabled(PSTATE.EL) then inst_type = if use_key_a then GCSInstType_PRETAA else GCSInstType_PRETAB; target = LoadCheckGCSRecord(target, inst_type); SetCurrentGCSPointer(GetCurrentGCSPointer() + 8); end; // Value in BTypeNext will be used to set PSTATE.BTYPE BTypeNext = '00'; let branch_conditional : boolean = FALSE; BranchTo{64}(target, BranchType_RET, branch_conditional);
2026-03_rel 2026-03-26 20:48:11
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